Abstract
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS,
VOL. 13,
Q01007,
11 PP., 2012
doi:10.1029/2011GC003807
Disentangling the Hettangian carbon isotope record: Implications for the aftermath of the end-Triassic mass extinction
- It concerns the interactions between biological events and carbon cycle
- It highlights a new major positive organic carbon isotope event
- It shows a perturbed carbon cycle during the end-Triassic post -crisis interval
Muséum National d'Histoire Naturelle, CNRS UMR 7207 Paleobiodiversité et Paléoenvironnements, CP38, 8 rue Buffon, F-75005 Paris, France
Institute of Geology, University of Lausanne, UNIL-Dorigny, Bâtiment Anthropole 3182, CH-1015 Lausanne, Switzerland
Institute of Mineralogy and Geochemistry, University of Lausanne, Bâtiment Anthropole 3182, CH-1015 Lausanne, Switzerland
Department of Geosciences, Princeton University, 219 Guyot Hall, Princeton, New Jersey 08544, USA
NW Museum of Natural History, 5004 SW Lowell Street, Portland, Oregon 97221, USA
Section of Earth and Environmental Sciences, University of Geneva, rue des Maraîchers 13, CH-1205 Geneva, Switzerland
Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA
This study provides an organic carbon stable isotope (δ13Corg) record calibrated with detailed ammonite biostratigraphy, following the end-Triassic biological crisis. Precise correlation between this crucial fossil group and the δ13Corg record is key to understanding feedbacks between biological and environmental events following mass extinction. The latest Triassic and Hettangian δ13Corg record shows several negative and positive excursions. The end-Triassic negative shift coinciding with the mass extinction interval is followed by a positive excursion in the earliest Hettangian Psiloceras spelae beds, which marks the onset of recovery in the marine ecosystem. This positive trend is interrupted by a second negative δ13Corg excursion in the P. pacificum beds related to a minor ammonite extinction event. This pattern of the δ13Corg curve culminates in the uppermost Hettangian Angulata Zone major positive excursion. This indicates that both the ecosystem and the carbon cycle remained in a state of perturbation for at least 2 Ma, although the recovery of some pelagic taxa already began at the base of Jurassic. The early and late Hettangian positive δ13Corg excursions have been confused in several recent papers. Here, we show that during the Hettangian there are indeed two distinct positive δ13Corg excursions. Phases of anoxia and further pulses of Central Atlantic Magmatic Province volcanism during the Hettangian might have inhibited the full recovery for that interval of time. The main Liasicus-Angulata organic positive CIE (carbon isotope excursion) during the Late Hettangian might be related to gradual decreasing of pCO2 due to protracted high organic burial, and coincides with a second phase of recovery, as indicated by a pulse of ammonoid diversification.
Received 19 July 2011; accepted 22 November 2011; published 14 January 2012.
Citation: (2012), Disentangling the Hettangian carbon isotope record: Implications for the aftermath of the end-Triassic mass extinction, Geochem. Geophys. Geosyst., 13, Q01007, doi:10.1029/2011GC003807.
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